1. Field of the Invention
The invention is related to a radiation measurement system comprising first conversion means with an electrical port and an optical port, the optical port being coupled to a first end of an optical fiber, a second end of the optical fiber being coupled to an optical port of second conversion means placed within a dipole antenna comprising two hollow conductors, the electrical port of the second converter being coupled to the dipole antenna.
The invention is also related to an antenna suitable for use in such a measurement system.
2. Description of the Related Art
A measurement system according to the preamble is known from U.S. Pat. No. 4,091,327.
Such measurement systems are used for accurate measurements in the EMC (Electro Magnetic Compatibility) field. Such measurements include the determination of the emission of spurious EM fields by all kinds of electric equipment, or the susceptibility of such equipment to external EM fields. In order to obtain meaningful results from such measurements, antennas having well known properties are required. To meet this requirement, often dipole antennas are used, because their behavior is well known. A problem is that the properties of the antenna can be disturbed by the cable used to connect the antenna to the test equipment, the balun used to connect the symmetric antenna to the asymmetric cable, and other peripherals surrounding the antenna.
To eliminate the disturbing influences of said cable it is proposed in the above mentioned US patent to use converter means having an electrical port and an optical port inside the hollow dipole antenna. The optical part is coupled via an optical fiber to converter means having an optical part and an electrical part. In said known measurement system, the converter means inside the dipole antenna is an electro-optical converter which converts the (amplified) signal received by the dipole antenna into an optical signal which is transmitted via the optical fiber to the test equipment. In said known arrangement the (electrical) symmetry is disturbed due to the wiring near the dipole gap for connecting the dipole to the amplifier present in one part of the dipole antenna. This will result in an asymmetric radiation pattern of the antenna.